These are the commercial jet engines you see, like the Boeing 777, 747, Airbus A330 and A380s. Though there is a considerable reduction of the engine thrust, at these altitudes the lower drag associated with low air density means a more economical flight with a higher True Air Speed.
Crepitus in the knees may be caused by knee injuries such as meniscus tears. These are fairly common in people who play sports, jog, or run. A meniscus tear can cause crepitus as the joint moves. Chondromalacia patella is a dull ache behind the kneecap, usually caused by overuse or injury. There will be damage to the undersurface cartilage covering the kneecap.
What causes posterior tibial tendonitis or tears? Posterior tibial tendon problems can occur for a variety of reasons, including: 1  Overuse: Overuse symptoms occur after activities that use the tendon, such as walking, hiking or climbing stairs, especially when a person is not used to such activities.n most cases, the symptoms of posterior tibial tendonitis develop gradually. When the tendon tears, the symptoms are more obvious. Symptoms may include the following: 1  Pain and swelling on the inside of the ankle. 2  Loss of the arch and the development of a flatfoot. 3  A rolling of the ankle and foot inwards.